There has been known a hollow structure, such as the structure disclosed in Japanese patent publication No. H08-112873 for example. Japanese patent publication No. H08-112873 discloses a foamed hollow structure, in which a highly expandable thermoplastic resin composition is filled into each square-shaped hollow recess of a thermoplastic resin body having a lattice-like horizontal sectional configuration. The thermoplastic resin body is then heated to cause volume expansion of the highly expandable thermoplastic resin composition, so as to obtain the foamed hollow structure.
Recently, a technology of producing a hollow structure having a plurality of regularly-arranged hollow parts is being developed. The hollow structure having the regularly-arranged hollow parts is formed by regularly forming gas-retaining spaces, which stores gas therein, to a substrate, and forming a flat plastic-deformation film, which includes a plastic-deformable material, on a surface of the substrate. Then, the plastic-deformation film is expanded and extended by expanding pressure of the gas inside of the gas-retaining spaces, so as to obtain the hollow structure having the regularly-arranged hollow parts. Such a technology is, for example, described in Japanese patent publication No. 2007-98930.